Le Fanu was a bit more difficult to read than James; he is an older writer, writing in the mid 19th century, and I think that contributes to some of it. His sentences, while well constructed and with excellent diction and syntax, were less fluid than James and so sometimes made for clunky reading. This story was quite good, despite those difficulties, and yet I think it would have been far scarier in the time in which it was written. The pay off depended upon a scientific, medical explanation, which nowadays sounds ridiculous. But if one did not know any better, as say one might not in the mid 19th century, then the result would likely be downright terrifying.
Summary: A man is called upon, because of a certain expertise, to attend to a Reverend who has been having trouble lately of a most peculiar nature. He cannot complete his prayers or say the Mass without suddenly stopping and praying fervently and quickly to himself. The cause, it turns out, is a demon is tormenting him, a demon in the shape of a monkey. It will not leave him alone, waking or sleeping, and is with him always. From time to time it will disappear for weeks on end, but it always returns right at the most inopportune time. In the end, he can stand it no longer.
Personal Fright: 2/10
General Horror/Oppressiveness: 6/10